Travelling-wave tube with connectors for the end turns of the helix



1963 T. w. H. FOKKER ETAL 3,114,857

TRAVELLINGWAVE TUBE WITH CONNECTORS FOR THE END TURNS OF THE HELIX FiledJuly 15. 1960 INVENTORS THEODORUS WILHELMUS HENDRICUS FOKKER JOHANGERARD VAN WIJNGAARDEN ARIE VERSNEL AQM United States Patent 3,114,857TRAVELLHJG-WAVE TUBE WITH CONNECTORS FOR THE END TURNS OF THE HELEXTheodorus Wiihelmus Hendricns Fokker, Hilversum, and

Johan Gerard van Wijngaarden and Arie Versnel, Eindhoven, Netherlands,assignors to North American Philips Company, lac, New York, N.Y., acorporation of Delaware Filed duly 15, 1960, Ser. No. 43,056 Claimspriority, application Netherlands July 17, 1959 2 Claims. (Cl. 315--3.5)

This invention relates to travelling-wave tubes in which the electronbeam is in interaction with a helical conductor having its ends securedto disc-shaped or annular conductors which are directed at right anglesto the axis of the tube and which close the apertures of the wave-guidesto which the tube is coupled.

Structures of the above-mentioned kind are already known. In suchstructures the coupling between the helix and the hollow wave-guide isnot wholly sufiicient. The annular conductor sometimes has anaxially-directed portion to which the helical conductor is connected.However, this involves the disadvantage that the electron beam extendsover part of its path in an asymmetric potential field, which gives riseto heating of the conductors due to striking electrons and to chargingof ceramic supports present in the surroundings.

Similar ditficulties as mentioned above likewise occur if the end of thehelical conductor has a portion extending in an axial direction.

An object of the invention is to provide a structure which affordsadvantages with respect to known tubes.

According to the invention, in a travelling-wave tube in which theelectron beam is in interaction with a helical conductor having its endsconnected to disc-shaped or annular conductors directed at right anglesto the axis of the tube, conductors are provided, one at each end of thehelical conductor, which extend substantially parallel to the axis ofthe helical conductor at same distance outside it and which areconnected, on the one hand, to the disc-shaped or annular conductor towhich the helical conductor is connected and, on the other hand, to apoint remote several turns from the end of the helical conductor.

In a structure according to the invention, it is achieved that theelectron beam extends throughout its length in a symmetrical potentialfield so that electrons are not unnecessarily lost from the beam andcharging of ceramic supports in the surroundings does not occur, whilstalso proper matching of the helix to the waveguides to be connected tothe tube may readily be achieved.

A structure is already known in which, as reckoned from the end of thehelical conductor, a straight conductor extends towards an annularconductor positioned more towards the .centre of the tube, but in thiscase the helical conductor does not extend to the vicinity of theconductors closing the waveguides to which the tube is connected.

A structure is also known in which a conductor extends through theinsulating wall of the tube, at a point located several turns from theend, at right angles to the helix and terminates in a wave-guide. Inthis case also, the helical conductor does not extend far enough at itsends.

In order that the invention may be readily carried into 3,114,857Patented Dec. 17, 1963 effect, one embodiment thereof will now beexplained in detail, by way of example, with reference to theaccompanying diagrammatic drawing, in which:

FIG. 1 shows a longitudinal section of a travellingwave tube accordingto the invention,

FIG. 2 shows a cross-section in the direction of arrows 11-11 in FIG. 1;and

FIG. 3 is .a cross section in the direction of the arrows IlIIlI in FIG.1.

In FIG. 1, reference numeral 1 indicates the glass wall of thetravelling-wave tube which is provided with two lead-through discs 2 and3. Secured to the disc 2 by means of a cylindrical transition piece 4 isa helical conductor 5 which is supported by three ceramic rods 6provided with a number of cuts corresponding to the pitch of the helix.The helical conductor is surrounded by mica plates 8 and 21 which arecovered with damping material 9 and 22, respectively, and which are atright angles to the plane of the drawing near the cathode half of thehelix and parallel to the drawing near the output half of the helix. Theplates 8 (FIG. 2) and plates 21 (FIG. 3) are supported in mica discs 10p0- sitioned at right angles to the axis of the tube and held togetherby means of two ceramic rods 11. The plates 8 and plates 21 aresupported in the direction of their length by means of mica plates 12and 23, respectively.

Provided in the lead-through disc 3 is a transition piece 13 to whichthe other end of the helical conductor 5 is secured.

At each end of the helical conductor there is provided a conductor 14connected to the transition piece and to a point about three turns fromthe end.

A glass portion 15 contains an electron gun 16 and an acceleratingelectrode 17. A glass cylinder 18 insulates a collecting electrode 19from lead-through disc 3. The heat produced in collecting electrode 19is dissipated by natural cooling of cooling fins 20.

What is claimed is:

1. An electron discharge device comprising an evacuated envelope, meanswithin said envelope to produce a beam of electrons, a collectorelectrode in the path of the beam of electrons, a helical conductorbetween the electron beam producing means and the collector elecrode andsurrounding the electron beam, an annular conductor transverse to thepath of the electron beam between each of the ends of said helicalconductor and beam producing means and the collector electroderespectively to which the ends of said helical conductor are connected,and conductor means positioned parallel to the path of the electron beamconnecting each of said annular conductors to said helical conductorseveral turns remote from each end thereof,

2. A travelling-wave tube as claimed in claim 1 in which the helicalconductor is arranged between two sets of parallel plates which arecovered with damping material, said sets of parallel plates being atright angles to each other in the two halves of the tube.

References Cited in the file of this patent UNITED STATES PATENTS2,584,802 Hansell Feb. 5, 1952 2,595,698 Peter May 6, 1952 2,742,588Hollenberg Apr. 17, 1956 2,798,183 Sensiper July 2, 1957 2,850,666Brewer Sept. 2, 1958

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AN EVACUATED ENVELOPE, MEANSWITHIN SAID ENVELOPE TO PRODUCE A BEAM OF ELECTRONS, A COLLECTORELECTRODE IN THE PATH OF THE BEAM OF ELECTRONS, A HELICAL CONDUCTORBETWEEN THE ELECTRON BEAM PRODUCING MEANS AND THE COLLECTOR ELECRODE ANDSURROUNDING THE ELECTRON BEAM, AN ANNULAR CONDUCTOR TRANSVERSE TO THEPATH OF THE ELECTRON BEAM BETWEEN EACH OF THE ENDS OF SAID HELICALCONDUCTOR AND BEAM PRODUCING MEANS AND THE COLLECTOR ELECTRODERESPECTIVELY TO WHICH THE ENDS OF SAID HELICAL CONDUCTOR ARE CONNECTED,AND CONDUCTOR MEANS POSITIONED PARALLEL TO THE PATH OF THE ELECTRON BEAMCONNECTING EACH OF SAID ANNULAR CONDUCTORS TO SAID HELICAL CONDUCTORSEVERAL TURNS REMOTE FROM EACH END THEREOF.